1. Field of the Invention
An aspect of the present invention relates to a duplex image forming apparatus and a duplex image forming method. More particularly, an aspect of the present invention relates to a duplex image forming apparatus and a duplex image forming method, which efficiently feeds a recording medium by shortening a feeding path of the recording medium.
2. Description of the Related Art
Generally, an image forming apparatus such as a duplicator, a printer and a facsimile includes, for example, an image bearing body employed with a photoconductive drum, an electrostatic latent image forming unit, a developing unit developing the electrostatic latent image on the photoconductive drum and visualizing a developed image, a transferring unit transferring the developing agent image on the photoconductive drum to a middle transfer belt or a recording medium (i.e., paper, transparency, etc.), and a fixing unit heating and compressing the image transferred on the recording medium through the transferring unit to a high temperature and pressure to permanently fix the image on the recording medium. The image forming apparatus also generally has a duplex printing unit to consecutively print desired information on both surfaces of one sheet of recording medium (hereinafter referred to as a (or the) “recording medium”).
FIG. 1 is provided to explain an operation of a conventional duplex printing image forming apparatus. As shown in FIG. 1, a pick-up roller 3 rotates and a recording medium 7 is picked up through a recording medium receiving unit 5. The picked-up recording medium 7 is fed to a recording medium supplying path 11 by a feeding roller 9.
When a registration sensor 13 senses that a front end of the fed recording medium 7 reaches a particular position, a registration roller 15 stops for a predetermined time and lines up the front end of the recording medium 7. If the registration roller 15 rotates and the recording medium 7 is fed, a feeding sensor 17 senses the front end of a first recording medium 7 and an image forming unit 20 operates after a predetermined time.
If an image is formed on one surface of the recording medium 7 through the image forming unit 20, the image transferred on the recording medium 7 through a fixing unit 19 is fixed on the recording medium 7 by fusing.
If the recording medium 7 exits a predetermined section through an exiting and reversing roller 23 formed on a direct exit path 21, a feeding direction of the recording medium 7 is reversed at a recording medium turning point S and the recording medium 7 is fed to a duplex feeding path 24.
The exiting and reversing roller 23 then rotates either counterclockwise to discharge the recording medium through the direct exiting path 21 from the image forming apparatus, or clockwise to reverse the path of the recording medium 7 at the recording medium turning point S so as feed the recording medium 7 into the duplex feeding path 24.
The recording medium 7 is then fed through duplex feeding rollers 25, 27 formed on the duplex feeding path 24 and reenters the recording medium supplying path 11, so that a duplex image may be formed on the as yet unprinted side of the recording medium 7.
Based on the structure, the pick-up roller 3, the feeding roller 9, the registration roller 15 and the image forming unit 20 are driven by a main motor 31 via a main driving system 30.
The fixing unit 19, the exiting and reversing roller 23 and the duplex transfer rollers 25, 27 are driven by an exiting and reversing driving system 50 driven by an exiting and reversing motor 51.
As is abovementioned, however, the conventional duplex image forming apparatus forms images on both surfaces of the first recording medium, and the image on one surface of a second recording medium so inconveniently that image output efficiency per minute of printing decreases.